Problem: Evaluate the following expression when $x = 4$ and $y = 10$. $10$ $x$ $ + 7$ $y$ $ - 9$
Solution: Substitute $4$ for ${x}$ and $10$ for ${y}$ $ = 10{(4)} + 7{(10)} - 9 $ $ = 40 + 70 - 9 $ $ = 101$